The 3rd generation partnership project (3GPP) currently specifies the so-called “IMS centralized services” (ICS). The stage 2 description is given e.g. in technical specification (TS) 23.292. The basic idea is to centralize the service control in the 3GPP internet protocol multimedia subsystem (IMS, see e.g. 3GPP TS 23.228 and 24.229) independent from the access type being used, i.e. even if the serving access network for a speech bearer is in a 3GPP circuit switched (CS) domain.
The TS 23.292 defines e.g. the MSC server enhanced for ICS. Such an enhanced MSC server allows a user equipment (UE) (including e.g. a legacy global system for mobile communications (GSM) UE) to obtain services provided e.g. by the IMS without having any ICS specific functionalities. The MSC server enhanced for ICS may provide for interworking of user-network signaling received over the CS access (e.g. A/Iu and E interface) to IMS SIP (Session Initiation Protocol) and vice versa. This also covers e.g. registration and de-registration in the IMS on behalf of the UE.
There have been approaches addressing the above functionalities.
One such approach is described e.g. in section 7.2.1.2 ‘Registration using I2 reference point’ of TS 23.292, namely the registration procedure when the UE moves (or performs e.g. international mobile subscriber identity (IMSI) attach) towards a MSC Server enhanced for ICS.
FIG. 1 corresponds to FIG. 7.2.1.2-1 in TS 23.292, and shows a communication network 100 that may comprise a UE 101 and a network (not shown). In turn, the network may comprise an MSC server 1021, an optional interrogating call session/state control function (I-CSCF) 1022, a serving CSCF (S-CSCF) 1023, a home subscriber server/home location register (HSS/HLR) 1024 and a service centralization and continuity application server (SCC AS) 1024.
FIG. 1 shows how e.g. IMS registration is performed by the MSC Server enhanced for ICS e.g. upon CS attach.
In step 1, the UE 101 may initiate CS attach procedures towards the CS network.
In step 2, e.g. the MSC server 1021 and the HSS/HLR 1024 being part of the CS network may perform CS location update, authentication and obtaining subscriber data.
In step 3, e.g. the MSC server 1021 may return a CS attach accept to UE 101.
In step 4, e.g. the MSC server 1021 may decide to initiate an IMS registration for this subscriber.
In step 5, e.g. the MSC server 1021 may derive a domain name from the subscriber's identity (e.g. IMSI) and may discover the address of the appropriate I-CSCF/interconnection border control function (IBCF).
In step 6, e.g. the MSC server 1021 may transmit e.g. a SIP REGISTER message to the IMS (e.g. to the I-CSCF 1022) with a private and temporary public user identity derived from the subscriber's IMSI as well as an InstanceID. The REGISTER message may also contain information indicating the capabilities and characteristics of the MSC server 1021 as a SIP User Agent Client. E.g. the I-CSCF 1022 may verify that the incoming REGISTER message origins from a trusted MSC server (in the same way the I-CSCF 1022 would check that a normal REGISTER message origins e.g. from a trusted proxy CSCF (P-CSCF)).
In step 7, e.g. the I-CSCF 1022 may initiate procedures for location/allocation of the S-CSCF 1023.
In step 8, e.g. the I-CSCF 1022 may forward the REGISTER message e.g. to the S-CSCF 1023.
In step 9, e.g. the S-CSCF 1023 may identify the REGISTER message as being from the MSC server 1021. The S-CSCF 1023 may skip any further authentication procedures and may perform registration procedures e.g. with the HSS/HLR 1024.
In step 10, e.g. the S-CSCF 1023 may perform service control execution procedures. For example, filter criteria may direct the S-CSCF 1023 to transmit a REGISTER message e.g. to the SCC AS 1025.
Finally, in step 11, the IMS registration procedures are completed.
In addition, e.g. section 7.2.1.3 ‘Deregistration using I2 reference point’ of TS 23.292 describes the de-registration procedure when the UE 101 moves from a MSC Server 1021 enhanced for ICS towards a MSC server (not shown) not enhanced for ICS.
FIG. 2 corresponds to FIG. 7.2.1.3-1 in TS 23.292, and may comprise the UE 101, the network (not shown), the MSC server 1021, the optional I-CSCF 1022, the S-CSCF 1023, the HSS/HLR 1024 and the SCC AS 1025 already described herein above in conjunction with FIG. 1. Furthermore, as shown in FIG. 2, the network may further comprise a visited MSC (VMSC) 1021′.
FIG. 2 shows how IMS de-registration may be performed by the MSC Server 1021 enhanced for ICS upon detection of the location cancellation procedure. Identical IMS deregistration procedures may be initiated by the MSC Server 1021 enhanced for ICS upon receipt of any other indication that the UE 101 may be no longer considered active at this MSC/visited location register (VLR).
In step 1, e.g. the UE 101 may initiate location updating procedures towards the CS network, e.g. the VMSC 1021′.
In step 2, e.g. the VMSC 1021′ and the HSS/HLR 1024 being part of the CS network may perform CS location updating and authentication procedures.
In step 3, e.g. the HSS/HLR 1024 may initiate location cancellation procedures e.g. towards the old VLR/MSC server 1021.
In step 4, e.g. the MSC server 1021 may initiate IMS de-registration for this subscriber (e.g. UE 101) by transmitting e.g. a SIP REGISTER message e.g. with an expiration time of zero seconds to the I-CSCF 1022.
In step 5, e.g. the I-CSCF 1022 may initiate procedures for location of the S-CSCF 1023.
In step 6, e.g. the I-CSCF 1022 may forward the REGISTER message to the S-CSCF 1023.
In step 7, e.g. the S-CSCF 1023 may identify the REGISTER message as being from the MSC server 1021 which is a trusted network node. The S-CSCF 1023 may perform deregistration procedures with the HSS/HLR 1024.
In step 8, e.g. the S-CSCF 1023 may perform service control execution procedures. For example, filter criteria may direct the S-CSCF 1023 to transmit a REGISTER message to the SCC AS 1025.
Finally, in step 9, the IMS deregistration procedures are completed.
However, TS 23.292 does not describe the case when a UE moves from one MSC Server enhanced for ICS to another MSC Server enhanced for ICS. So, if registration is performed first, the de-registration procedure would delete the new registered contact address. In other words, TS 23.292 describes the registration and de-registration procedures in section 7.2. The de-registration procedure caused by a normal location update (UE has moved to another Location Area) from one MSC Server enhanced for ICS towards a MSC Server without this enhancement is described in section 7.2.1.3. A description when the UE moves to another MSC Server enhanced for ICS is not contained or mentioned in TS 23.292.
In consideration of the above, it is an object of examples of the present invention to overcome one or more of the above drawbacks. In particular, the present invention provides a method, an apparatus, a system and a related computer program product for handover management.
According to an example of the present invention, in a first aspect, this object is for example achieved by a method comprising:
accepting, after storage of a registration message comprising first address information received from a first serving entity capable of access technology-independent service control, a de-registration request message comprising second address information identical to the first address information from a second serving entity capable of access technology-independent service control.
According to further refinements of the example of the present invention as defined under the above first aspect,
the method further comprises storing the received registration message;                the method further comprises comparing the first and second address information with each other, and wherein the accepting is performed based on a result of the comparing;        the accepting is performed if at least one of the first and second serving entities is capable of enabling network entities different from the first and second serving entities to perform de-registration on behalf of a network terminal;        the method further comprises, prior to the accepting, receiving the de-registration message;        the method further comprises, after the receiving, deferring an interaction with a network subscriber server entity by a settable period of time;        if another registration message is received during the settable period of time, a portion of the interaction is performed;        the first and second address information are constituted by an internet protocol address for session initiation protocol signaling;        the internet protocol address for session initiation protocol signaling is comprised in a contact header;        the first and second serving entities are constituted by mobile switching center servers;        the access technology-independent service control is constituted by internet protocol multimedia subsystem centralized services.        
According to an example of the present invention, in a second aspect, this object is for example achieved by an apparatus comprising:                means for accepting, after storage of a registration message comprising first address information received from a first serving entity capable of access technology-independent service control, a de-registration request message comprising second address information identical to the first address information from a second serving entity capable of access technology-independent service control.        
According to further refinements of the example of the present invention as defined under the above second aspect,                the apparatus further comprises means for storing the received registration message;        the apparatus further comprises means for comparing the first and second address information with each other, and wherein the means for accepting is configured to accept based on a result from the means for comparing;        the means for accepting is configured to accept if at least one of the first and second serving entities is capable of enabling network entities different from the first and second serving entities to perform de-registration on behalf of a network terminal;        the apparatus further comprises means for receiving the de-registration message prior to the accepting performed by the means for accepting;        the apparatus further comprises means for deferring, after the receiving performed by the means for receiving, an interaction with a network subscriber server entity by a settable period of time;        the apparatus further comprises means for performing, if another registration message is received during the settable period of time, a portion of the interaction;        the first and second address information are constituted by an internet protocol address for session initiation protocol signaling;        the internet protocol address for session initiation protocol signaling is comprised in a contact header;        the first and second serving entities are constituted by mobile switching center servers;        the access technology-independent service control is constituted by internet protocol multimedia subsystem centralized services;        the apparatus is constituted by a serving call session control function;        at least one, or more of means for accepting, means for comparing, means for receiving, means for deferring, means for performing and the apparatus is implemented as a chipset or module.        
According to an example of the present invention, in a third aspect, this object is for example achieved by a system comprising:
a first mobile switching center server capable of access technology-independent service control, for transmitting the registration message comprising the first address information,
a second mobile switching center server capable of access technology-independent service control, for transmitting the de-registration message comprising the second address information identical to the first address information; and
an apparatus according to the above second aspect.
According to an example of the present invention, in a fourth aspect, this object is for example achieved by a computer program product comprising code means for performing methods steps of a method according to the above first aspect, when run on a processing means or module.
In this connection, it has to be pointed out that examples of the present invention enable one or more of the following:                coping with overlapping registration and de-registration procedures when the UE moves between two MSC servers enhanced for ICS.        Preventing deletion of a newly registered contact address by the de-registration procedure, if registration of the new contact address is performed first.        Closing a gap in TS 23.292, which does not describe the case when a UE moves from one MSC Server enhanced for ICS to another MSC Server enhanced for ICS:        The critical issue in TS 23.292 resides in that there is no time correlation between registration (step 6 in FIG. 1) and de-registration (step 4 in FIG. 2).        TS 23.292 describes the registration and de-registration procedures in its section 7.2. The de-registration procedure caused by a normal location update (UE has moved to another location area) from one MSC server enhanced for ICS towards a MSC server without this enhancement is described in TS 23.292, section 7.2.1.3. However, any description of when the UE moves to another MSC server enhanced for ICS is not contained or mentioned in TS 23.292. So, the problem according to examples of the present invention has not yet been addressed.        